Method and system for managing metadata in a storage environment

ABSTRACT

Method and system is provided for managing metadata for a plurality of data containers that are stored at one or more storage volumes in a storage system. The metadata is collected from one or more storage volumes and then provided to a catalog module. The catalog module pre-processes the metadata and then generates a searchable data structure. The searchable data structure may then be used to respond to a user request for information regarding the storage system.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is related to U.S. patent application, entitled“METHOD AND SYSTEM FOR MANAGING METADATA IN A CLUSTER BASED STORAGEENVIRONMENT”; Ser. No. 12/706,953, filed on even date herewith and thedisclosure of which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to storage systems.

BACKGROUND

Various forms of storage systems are used today. These forms includedirect attached storage (DAS) network attached storage (NAS) systems,storage area networks (SANs), and others. Network storage systems arecommonly used for a variety of purposes, such as providing multipleusers with access to shared data, backing up data and others.

A storage system typically includes at least one computing systemexecuting a storage operating system for storing and retrieving data onbehalf of one or more client processing systems (“clients”). The storageoperating system stores and manages shared data containers in a set ofmass storage devices, such as magnetic or optical disks or tapes.

In traditional storage environments, the operating system is typicallygeared towards handling access to one object at a time. Access to agroup of data containers within a file system is difficult because theoperating system layout is such that metadata for data containers, forexample, a file name, attributes, access control lists, and informationregarding an owner of the data container may not be stored contiguouslyat a storage device and may be stored at different locations. Therefore,it is difficult for an operating system to respond to user queries forinformation regarding a data container or a group of data containersbecause one typically has to traverse through a namespace and perform anextensive directory search. The term namespace refers to a virtualhierarchical collection of unique volume names or identifiers anddirectory paths to the volumes, in which each volume represents avirtualized container storing a portion of the namespace descending froma single root directory. This is inefficient because metadatainformation is stored at various locations and also a directory may havea large number of files within a namespace. Continuous efforts are beingmade to integrate managing data containers and the metadata for the datacontainers.

SUMMARY

In one embodiment, a method and system is provided for managing metadatafor a plurality of data containers that are stored at one or morestorage volumes in a storage system. The metadata is collected from oneor more storage volumes and then provided to a catalog module. Thecatalog module pre-processes the metadata and then generates asearchable data structure. The searchable data structure may then beused to respond to a user request for information regarding the storagesystem.

In another embodiment, a machine implemented method for a storage systemis provided. The method includes configuring a data storage volume forcollecting metadata for a plurality of data containers stored at thedata storage volume. The metadata includes at least an attribute that isassociated with the plurality of data containers. A storage volume isconfigured to operate as a catalog volume for storing metadataassociated with the plurality of data containers. The metadata for theplurality of data containers is collected and pre-processed byextracting one or more fields. The pre-processed metadata is stored in asearchable data structure at the catalog volume for responding to a userquery requesting information regarding the plurality of data containers.

In yet another embodiment, a machine implemented method for a storagesystem for storing a plurality of data containers at one or more storagevolumes is provided. The method includes pre-processing metadataassociated with the plurality of data containers where the metadataincludes an attribute that is associated with the plurality of datacontainers. A searchable data structure is then generated by indexingthe pre-processed metadata such that information related to theplurality of data containers is obtained regardless of a storage volumelocation.

In another embodiment, a machine implemented method for a storage systemfor storing a plurality of data containers at one or more storagevolumes is provided. The method includes indexing metadata associatedwith the plurality of data containers where the metadata includes anattribute that is associated with the plurality of data containers andthe metadata is collected from at least one storage volume. The indexedmetadata is then stored in a searchable data structure which may be usedfor obtaining information regarding the plurality of data containers.The searchable data structure stores a snapshot table identifier foridentifying a snapshot when the plurality of data containers werereplicated and a time stamp when the snapshot was taken.

This brief summary has been provided so that the nature of thisdisclosure may be understood quickly. A more complete understanding ofthe disclosure can be obtained by reference to the following detaileddescription of the various embodiments thereof in connection with theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features and other features will now be described withreference to the drawings of the various embodiments. In the drawings,the same components have the same reference numerals. The illustratedembodiments are intended to illustrate, but not to limit the presentdisclosure. The drawings include the following Figures:

FIG. 1A shows a block diagram of a storage environment, managedaccording to one embodiment;

FIG. 1B shows an example of a management application used for managingthe storage environment of FIG. 1A, according to one embodiment;

FIG. 2 shows an example of a storage environment with a cluster system,managed according to one embodiment;

FIGS. 3A and 3B show examples of a storage operating system, usedaccording to one embodiment;

FIG. 3C shows an example of an aggregate, used according to oneembodiment;

FIG. 3D shows an example of a namespace used according to oneembodiment;

FIG. 4A shows an example of a catalog system, according to oneembodiment;

FIG. 4B shows an example of the catalog system used in a clusteredstorage environment, according to one embodiment;

FIGS. 4C-4F show examples of different data structures used by thecatalog system, according to one embodiment;

FIGS. 5A-5C show process flow diagrams, according to the variousembodiments of the present disclosure;

FIG. 6 shows an example of a node used in a cluster system, according toone embodiment; and

FIG. 7 shows an example of a computing system for implementing theprocess steps of the present disclosure.

DETAILED DESCRIPTION

Definitions:

The following definitions are provided as they are typically (but notexclusively) used in the computing/storage environment, implementing thevarious adaptive embodiments described herein.

“Aggregate” is a logical aggregation of physical storage, i.e., alogical container for a pool of storage, combining one or more physicalmass storage devices (e.g., disks) or parts thereof into a singlelogical storage object, which includes or provides storage for one ormore other logical data sets at a higher level of abstraction (e.g.,volumes).

“CIFS” means the Common Internet File System Protocol, an accessprotocol that client systems use to request file access services fromstorage systems over a network.

“Data Container” means a block, a file, a logical unit of data or anyother information.

“FC” means Fibre Channel, a high-speed network technology primarily usedfor storage networking. Fibre Channel Protocol (FCP) is a transportprotocol (similar to Transmission Control Protocol (TCP) used inInternet Protocol (“IP”) networks) which predominantly transports SCSIcommands over Fibre Channel networks.

“iSCSI” means the Internet Small Computer System Interface, an IP basedstorage networking standard for linking data storage facilities. Thestandard allows carrying SCSI commands over IP networks. iSCSI may beused to transmit data over local area networks (LANs), wide areanetworks (WANs), or the Internet and can enable location-independentdata storage and retrieval.

“Metadata” refers to one or more attributes for a data container, forexample, a directory or data file. The attributes include (a) a uniquedata container identifier, for example, an inode number; (b) a datacontainer type, i.e., if the data container is a directory, file andothers; (c) information regarding whether the data container wascreated, modified or deleted; (d) a data container name (for example,NFS file name and CIFS file name) and path; (e) an owner identifier, forexample, an NFS user identifier or a CIFS owner identifier; (f) a groupidentifier, for example, an NFS group identifier (GID); (g) a datacontainer size; (h) permissions associated with the data container, forexample, NFS permission bits that provide information regardingpermissions associated with the data container; (i) time the datacontainer was accessed (access time); (j) time the data container wasmodified (modification time); (k) time the data container was created(creation time), when applicable; and (l) any other custom fields thatmay be specified by a user or a storage system, for example, accesscontrol lists (ACLS) or a named stream which is a CIFS level featurethat connects a file to a directory or any other attribute.

“Namespace” refers to a virtual hierarchical collection of unique volumenames or identifiers and directory paths to the volumes, in which eachvolume represents a virtualized container storing a portion of thenamespace descending from a single root directory. For example, eachvolume associated with a namespace can be configured to store one ormore data files, scripts, word processing documents, executable programsand others. In a typical storage system, the names or identifiers of thevolumes stored on a storage server can be linked into a namespace forthat storage server. The term global namespace refers to a virtualhierarchical collection of unique volume names or identifiers anddirectory paths to the volumes, in which the volumes are stored onmultiple server nodes within a clustered storage server system. The termvirtual in this context means a logical representation of an entity.

“NFS” means Network File System, a protocol that allows a user to accessstorage over a network.

“Snapshot” (without derogation to any trademark rights of NetApp, Inc.)means a point in time copy of a storage file system. A snapshot is apersistent point in time image of an active file system that enablesquick recovery of data after data has been corrupted, lost, or altered.Snapshots can be created by copying the data at each predetermined pointin time to form a consistent image, or virtually by using a pointer toform the image of the data.

“Volume” is a logical data set which is an abstraction of physicalstorage, combining one or more physical mass storage devices (e.g.,disks) or parts thereof into a single logical storage object, and whichis managed as a single administrative unit, such as a single filesystem. A volume is typically defined from a larger group of availablestorage, such as an aggregate.

As used in this disclosure, the terms “component”, “module”, “system,”and the like are intended to refer to a computer-related entity, eithersoftware-executing general purpose processor, hardware, firmware and acombination thereof. For example, a component may be, but is not limitedto being, a process running on a processor, a processor, an object, anexecutable, a thread of execution, a program, and/or a computer.

By way of illustration, both an application running on a server and theserver can be a component. One or more components may reside within aprocess and/or thread of execution, and a component may be localized onone computer and/or distributed between two or more computers. Also,these components can execute from various computer readable media havingvarious data structures stored thereon. The components may communicatevia local and/or remote processes such as in accordance with a signalhaving one or more data packets (e.g., data from one componentinteracting with another component in a local system, distributedsystem, and/or across a network such as the Internet with other systemsvia the signal).

Computer executable components can be stored, for example, on computerreadable media including, but not limited to, an ASIC (applicationspecific integrated circuit), CD (compact disc), DVD (digital videodisk), ROM (read only memory), floppy disk, hard disk, EEPROM(electrically erasable programmable read only memory), memory stick orany other storage device, in accordance with the claimed subject matter.

Storage Environment 100:

FIG. 1A shows an example of a non-cluster based storage environment 100where the various embodiments disclosed herein may be implemented.Storage environment 100 is used to store a plurality of data containersacross a plurality of storage devices. The embodiments disclosed hereinprovide a catalog system that collects metadata for the plurality ofdata containers, pre-processes the collected metadata and stores thepre-processed information in one or more searchable data structures, forexample, a relational database. The searchable data structure may thenbe used to search for information regarding the plurality of datacontainers and respond to user queries with respect to the stored datacontainers.

Storage environment 100 may include a plurality of storage systems 108,each coupled to a storage subsystem 111. A storage subsystem 111 mayinclude multiple mass storage devices 112 a-112 n (may also be referredto as 112) that may be used to store a plurality of data containers (forexample, directory files and data files) as well as the searchable datastructure, as described below. The mass storage devices in each storagesubsystem 111 may be, for example, conventional magnetic disks, opticaldisks such as CD-ROM or DVD based storage, magneto-optical (MO) storage,flash memory storage device or any other type of non-volatile storagedevices suitable for storing data.

Each storage subsystem 111 is managed by a corresponding storage system108. The storage devices in each storage subsystem 111 can be organizedinto one or more redundant array of inexpensive disks (“RAID”) groups,in which case the corresponding storage system 108 accesses the storagesubsystem 111 using an appropriate RAID protocol.

Each storage system 108 may operate as a NAS based file server, ablock-based storage server such as used in a storage area network (SAN),or a combination thereof, or a node in a clustered environment describedbelow with respect to FIG. 2, or any other type of storage server. Notethat certain storage systems from NetApp Inc. in Sunnyvale, Calif., arecapable of providing clients with both file-level data access andblock-level data access.

Storage environment 100 may also include a plurality of client systems104.1-104.2 (may also be referred to as 104), a management console 120executing a catalog module 119 and at least one network 106 communicablyconnecting the client systems 104.1-104.2, storage system 108 andmanagement console 120. The client systems 104.1-104.2 may be connectedto the storage systems 108 via the computer network 106, such as apacket-switched network.

Clients 104.1-104.2 may be general purpose computers having a pluralityof components. These components may include a central processing unit(CPU), main memory, I/O devices, and storage devices (for example, flashmemory, hard drives and others). The main memory may be coupled to theCPU via a system bus or a local memory bus. The main memory may be usedto provide the CPU access to data and/or program information that isstored in main memory at execution time. Typically, the main memory iscomposed of random access memory (RAM) circuits. A computer system withthe CPU and main memory is often referred to as a host system.

Processors executing instructions in storage system 108 and clientsystems 104.1-104.2 communicate according to well-known protocols, suchas the NFS protocol or the CIFS protocol, to make data stored on disk112 appear to users and/or application programs as though the data werestored locally on the client systems 104.1-104.2. The storage system 108can present or export data stored on disks 112 as a volume, or one ormore qtree sub-volume units, to each of the client systems 104.1-104.2.Each volume may be configured to store data files, scripts, wordprocessing documents, executable programs, and the like. As describedbelow in more detail, a volume may be configured to operate as a“catalog volume” that stores a searchable data structure with metadatainformation regarding directories and data files stored on disks 112.

From the perspective of one of the client systems 104.1-104.2, eachvolume can appear to be a single disk drive. However, each volume canrepresent the storage space in one disk, an aggregate of some or all ofthe storage space in multiple disks, a RAID group, or any other suitableset of storage space.

Specifically, each volume can include a number of individuallyaddressable files. For example, in a NAS configuration, the files of avolume are addressable over the computer network 106 for file-basedaccess. In addition, an aggregate is a fixed-sized volume built on topof a number of RAID groups containing one or more virtual volumes orFlexVol® flexible volumes.

In a typical mode of operation, one of the client systems 104.1-104.2transmits one or more input/output commands, such as an NFS or CIFSrequest, over the computer network 106 to the storage system 108.Storage system 108 receives the request, issues one or more I/O commandsto storage device 112 to read or write the data on behalf of the clientsystem 104.1-104.2, and issues an NFS or CIFS response containing therequested data over the network 106 to the respective client system.

The management console 120 that executes storage management application(may also be referred to as management application) 118 may be, forexample, a conventional PC, workstation, or the like. In anotherembodiment, management application 118 may also be executed by storagesystem 108. The management application 118 may be a module withexecutable instructions, typically used by a storage networkadministrator to manage a pool of storage devices. Managementapplication 118 enables the administrator to perform various operations,such as monitoring and allocating storage space in the storage pool,creating and deleting volumes, directories and others.

In one embodiment, management application includes a catalog module 119that interfaces with storage system 108 for receiving metadata,pre-processes the collected metadata and then stores it in a searchablestructure, for example, a relational database 115. Although catalogmodule 119 is shown as a part of management application 118, it mayoperate as a standalone application or may also be integrated with theoperating system of storage system 108. Furthermore, although catalogmodule 119 is shown in the context of a NAS in FIG. 1A, it can be usedeffectively in a direct attached storage system (not shown) as well.

Communication between the storage management application 118, clients104 and storage systems 108 may be accomplished using any of the variousconventional communication protocols and/or application programminginterfaces (APIs), the details of which are not germane to the techniquebeing introduced here. This communication can be implemented through thenetwork 106 or it can be via a direct link (not shown) between themanagement console 120 and one or more of the storage systems 108.

One or more other storage-related applications may also be operativelycoupled to the network 106, residing and executing in one or more othercomputer systems 121. Examples of such other applications include databackup software, snapshot management software and others. It isnoteworthy that these applications may also be running at storage system108.

Storage Management Application 118:

FIG. 1B shows a block diagram of storage management application 118having catalog module 119, according to one embodiment. In theillustrated embodiment, the storage management application 118 may alsoinclude a graphical user interface (GUI) module 122 to generate a GUI(e.g., for use by a storage administrator); an Operations Manager 124for managing storage system 108, according to one embodiment; one ormore other management modules 126 to perform various other storagemanagement related functions; and a communication module 128.

The communication module 128 implements one or more conventionalcommunication protocols and/or APIs to enable the storage managementapplication 118 to communicate with the storage system 108 and clustersystem 114.

The storage management application 118 may also maintain policies 130, alist 132 of all volumes in a storage pool as well as a table 140 of allfree space (on a per-disk basis) in a storage pool. Policies 130 may beused to store configuration information, based on which metadata iscollected, pre-processed, indexed and then stored in database 115.Details regarding database 115 are provided below.

Clustered System:

The following describes a cluster based storage system (may also bereferred to as “clustered storage system” or “cluster storage system”)in a storage environment 200 of FIG. 2. The clustered system is ascalable, distributed architecture that stores data containers atdifferent storage devices that are managed by a plurality of nodes. Whenconfigured, metadata for each node is collected and provided to aninstance of catalog module 119 executed at each node. The metadata ispre-processed and then stored in a searchable format. More detailsregarding processing of metadata is provided below.

Storage environment 200 may include a plurality of client systems204.1-204.2 (may also be referred to as 204), a cluster storage system202, management console 120 and at least one computer network 206(similar to network 106) communicably connecting the client systems204.1-204.2 and a clustered storage system 202.

The clustered storage system 202 includes a plurality of nodes208.1-208.3 (may also be referred to as 208), a cluster switching fabric210, and a plurality of mass storage devices such as disks 212.1-212.3(may also be referred to as disks 212 (similar to storage 112). Each ofthe plurality of nodes 208.1-208.3 in the clustered storage system 202provides the functionality of a storage server. Clustered storagesystems like the clustered storage system 202 are available from NetApp,Inc.

Each of the plurality of nodes 208.1-208.3 may be configured to includean N-module, a D-module, and an M-host, each of which can be implementedas a separate software module. Specifically, node 208.1 includes anN-module 214.1, a D-module 216.1, and an M-host 218.1; node 208.2includes an N-module 214.2, a D-module 216.2, and an M-host 218.2; andnode 208.3 includes an N-module 214.3, a D-module 216.3, and an M-host218.3.

The N-modules 214.1-214.3 (may also be referred to as 214) includefunctionality that enables the respective nodes 208.1-208.3 to connectto one or more of the client systems 204.1-204.2 over the computernetwork 206, while the D-modules 216.1-216.3 (may also be referred to as216) connect to one or more of the disks 212.1-212.3. The D-modulesinterface with a metadata collection module (See FIG. 4B, 416) andprovides metadata for a plurality of data containers stored at one ormore of disks 212.

The M-hosts 218.1-218.3 (may also be referred to as 218) providemanagement functions for the clustered storage server system 202. In oneembodiment, each M-host 218 includes or interfaces with an instance ofcatalog module 119 (similar to 410, FIG. 4A) for receiving collectedmetadata, pre-processing the collected metadata and then storing theinformation is a searchable data structure.

A switched virtualization layer including a plurality of virtualinterfaces (VIFs) (may also be referred to a logical interfaces (LIFs))220 is provided between the respective N-modules 214.1-214.3 and theclient systems 204.1-204.2, allowing the disks 212.1-212.3 associatedwith the nodes 208.1-208.3 to be presented to the client systems204.1-204.2 as a single shared storage pool.

In one embodiment, the clustered storage system 202 can be organizedinto any suitable number of virtual servers (also referred to as“vservers”), in which each vserver represents a single storage systemnamespace with separate network access. Each vserver has a user domainand a security domain that are separate from the user and securitydomains of other vservers. Moreover, each vserver is associated with oneor more VIFs and can span one or more physical nodes, each of which canhold one or more VIFs and storage associated with one or more vservers.Client systems can access the data on a vserver from any node of theclustered system, but only through the VIFs associated with thatvserver. The interaction between a vserver and catalog module 119 isdescribed below with respect to FIG. 4B.

Each of the nodes 208.1-208.3 is defined as a computer adapted toprovide application services to one or more of the client systems204.1-204.2. In this context, a vserver is an instance of an applicationservice provided to a client system. The nodes 208.1-208.3 areinterconnected by the switching fabric 210, which, for example, may beembodied as a Gigabit Ethernet switch. Although FIG. 2 depicts an equalnumber (i.e., 3) of the N-modules 214.1-214.3, the D-modules216.1-216.3, and the M-Hosts 218.1-218.3, any other suitable number ofN-modules, D-modules, and M-Hosts may be provided. There may also bedifferent numbers of N-modules, D-modules, and/or M-Hosts within theclustered storage server system 202. For example, in alternativeembodiments, the clustered storage server system 202 may include aplurality of N-modules and a plurality of D-modules interconnected in aconfiguration that does not reflect a one-to-one correspondence betweenthe N-modules and D-modules.

The clustered storage server system 202 can include the NETAPP® DATAONTAP® storage operating system, available from NetApp, Inc., thatimplements the WAFL® storage system, or any other suitable storageoperating system.

The client systems 204.1-204.2 of FIG. 2 may be implemented asgeneral-purpose computers configured to interact with the respectivenodes 208.1-208.3 in accordance with a client/server model ofinformation delivery.

Each client system 204.1, 204.2 may request the services of one of therespective nodes 208.1, 208.2, 208.3, and that node may return theresults of the services requested by the client system by exchangingpackets over the computer network 206, which may be wire-based, opticalfiber, wireless, or any other suitable combination thereof. The clientsystems 204.1-204.2 may issue packets according to file-based accessprotocols, such as the NFS protocol or the CIFS protocol, when accessinginformation in the form of files and directories.

In a typical mode of operation, one of the client systems 204.1-204.2transmits an NFS or CIFS request for data to one of the nodes208.1-208.3 within the clustered storage server system 202, and the VIF220 associated with the respective node receives the client request. Itis noted that each VIF 220 within the clustered system 202 is a networkendpoint having an associated IP address, and that each VIF can migratefrom N-module to N-module. The client request typically includes a filehandle for a data file stored in a specified volume on one or more ofthe disks 212.1-212.3.

Specifically, each volume comprises a storage system subtree thatincludes an index node file (an inode file) having a root inode, and aset of directories and files contained under the root inode. Each inodeis a data structure allocated for a respective data file to storemetadata that describes the data file. For example, an inode can containdata and pointers for use in facilitating access to blocks of datawithin the data file, and each root inode can contain pointers to anumber of inodes.

Before describing the details of catalog module 119 and how itinterfaces with various components of storage environment 100 and 200,the following provides a description of a storage operating system thatmay be used in storage environment 100 and 200, according to oneembodiment.

Operating System:

FIG. 3A illustrates a generic example of an operating system 300executed by a node 208.1 (and/or storage system 108), according to oneembodiment of the present disclosure. Operating system 300 interfaceswith catalog module 119 via an interface 301. As described below in moredetail, operating system 300 provides metadata to catalog module 119 tobuild a searchable data structure.

In one example, operating system 300 may include several modules, or“layers” executed by one or both of N-Module 214 and D-Module 216. Theselayers include a file system manager 302 that keeps track of a directorystructure (hierarchy) of the data stored in storage devices and managesread/write operations, i.e. executes read/write operations on disks inresponse to client 204 requests.

Operating system 300 may also include a protocol layer 304 and anassociated network access layer 308, to allow node 208.1 to communicateover a network with other systems, such as clients 204 and storagemanagement application 118. Protocol layer 304 may implement one or moreof various higher-level network protocols, such as NFS, CIFS, HypertextTransfer Protocol (HTTP), TCP/IP and others, as described below.

Network access layer 308 may include one or more drivers, whichimplement one or more lower-level protocols to communicate over thenetwork, such as Ethernet. Interactions between clients 104 and massstorage devices 112 are illustrated schematically as a path, whichillustrates the flow of data through operating system 300.

The operating system 300 may also include a storage access layer 306 andan associated storage driver layer 310 to allow D-module 216 tocommunicate with a storage device. The storage access layer 306 mayimplement a higher-level disk storage protocol, such as RAID while thestorage driver layer 310 may implement a lower-level storage deviceaccess protocol, such as FC or SCSI. In one embodiment, the storageaccess layer 306 may implement the RAID protocol, such as RAID-4 orRAID-DP™ (RAID double parity for data protection provided by NetApp Inc.the assignee of the present disclosure).

In one embodiment, storage access layer 306 obtains metadata for variousdata containers that may be stored in a data volume and provides thatinformation to catalog module 119. The information is processed and thenstored in a searchable data structure, as described below.

FIG. 3B shows a detailed block diagram of the storage operating system300 that may be advantageously used with the present invention. In thisexample, the storage operating system comprises a series of processorexecutable layers organized to form an integrated network protocol stackor, more generally, a multi-protocol engine 325 that provides data pathsfor clients to access information stored on the node using block andfile access protocols. In addition, the storage operating systemincludes a series of processor executable layers organized to form astorage server 365 that provides data paths for accessing informationstored on the disks 212.1 of the node 208.1. Both the multi-protocolengine 325 and storage server 365 interface with the storage managementapplication 118 such that metadata for data containers stored at disks212 can be collected, processed and searched, according to oneembodiment.

N-blade 214 and D-blade 216 may interface with each other using CFprotocol 341. Both blades may also include interface 340 a and 340 b tocommunicate with other nodes and systems.

The multi-protocol engine includes a media access layer 312 (part oflayer 308, FIG. 3A) of network drivers (e.g., Gigabit Ethernet drivers)that interfaces to network protocol layers (part of layer 304, FIG. 3A),such as the IP layer 314 and its supporting transport mechanisms, theTCP layer 316 and the User Datagram Protocol (UDP) layer 315.

A file system protocol layer provides multi-protocol file access and, tothat end, includes support for the Direct Access File System (DAFS)protocol 318, the NFS protocol 320, the CIFS protocol 322 and the HTTPprotocol 324.

A virtual interface (“VI”) layer 326 implements the VI architecture toprovide direct access transport (DAT) capabilities, such as RDMA (RemoteDirect Memory Access), as required by the DAFS protocol 318. An iSCSIdriver layer 328 provides block protocol access over the TCP/IP networkprotocol layers, while a FC driver layer 330 receives and transmitsblock access requests and responses to and from the node. The FC andiSCSI drivers provide FC-specific and iSCSI-specific access control tothe blocks and, thus, manage exports of LUNS to either iSCSI or FCP or,alternatively, to both iSCSI and FCP when accessing the blocks on thenode 208.1.

The storage server 365 includes a file system module 302 in cooperatingrelation with a volume stripped module (VSM) 370, a RAID system module380 and a disk driver system module 390.

The VSM 370 illustratively implements a striped volume set (SVS). TheVSM 370 cooperates with the file system 302 to enable storage server 365to service a volume of the SVS.

The RAID system 380 manages the storage and retrieval of information toand from the volumes/disks in accordance with I/O operations, while thedisk driver system 390 implements a disk access protocol such as, e.g.,the SCSI protocol.

The file system 302 implements a virtualization system of the storageoperating system 300 through the interaction with one or morevirtualization modules illustratively embodied as, e.g., a virtual disk(vdisk) module (not shown) and a SCSI target module 335. The SCSI targetmodule 335 is generally disposed between the FC and iSCSI drivers 330,328 and the file system 302 to provide a translation layer of thevirtualization system between the block (lun) space and the file systemspace, where luns are represented as blocks.

The file system 302 is illustratively a message-based system thatprovides logical volume management capabilities for use in access to theinformation stored on the storage devices, such as disks.

The file system 302 illustratively may implement a write-anywhere filesystem having an on-disk format representation that is block-basedusing, e.g., 4 kilobyte (KB) blocks and using index nodes (inodes) toidentify data containers and metadata for the data container (such ascreation time, access permissions, size and others). The file systemuses data containers to store metadata describing the layout of its filesystem; these metadata data containers include, among others, an inodedata container. A data container handle, i.e., an identifier thatincludes an inode number (inum), may be used to retrieve an inode fromdisk.

Typically, the metadata as handled by file system 302 may not be storedcontiguously and may be spread out among different storage volumes. Thismakes it difficult for the file system to provide user requestedinformation that can be derived from the metadata. Hence, as describedbelow in more detail, the present catalog module 119 is being introducedto manage, organize and use the metadata for the data containers.

Broadly stated, all inodes of the write-anywhere file system areorganized into the inode data container. A file system (fs) info blockspecifies the layout of information in the file system and includes aninode of a data container that includes all other inodes of the filesystem. Each logical volume (file system) has an fsinfo block that ispreferably stored at a fixed location within, e.g., a RAID group. Theinode of the inode data container may directly reference (point to) datablocks of the inode data container or may reference indirect blocks ofthe inode data container that, in turn, reference data blocks of theinode data container. Within each data block of the inode data containerare embedded inodes, each of which may reference indirect blocks that,in turn, reference data blocks of a data container.

Operationally, a request from the client 204 is forwarded as a packetover the computer network 206 and onto the node 208.1. A network driverprocesses the packet and, if appropriate, passes it on to a networkprotocol and file access layer for additional processing prior toforwarding to the write-anywhere file system 302. Here, the file systemgenerates operations to load (retrieve) the requested data from disk 212if it is not resident “in core”, i.e., in memory 604 (FIG. 6).

If the information is not in memory, the file system 302 indexes intothe inode data container using the inode number (inum) to access anappropriate entry and retrieve a logical vbn. The file system thenpasses a message structure including the logical vbn to the RAID system380; the logical vbn is mapped to a disk identifier and disk blocknumber (disk,dbn) and sent to an appropriate driver (e.g., SCSI) of thedisk driver system 390. The disk driver 390 accesses the dbn from thespecified disk 212 and loads the requested data block(s) in memory forprocessing by the node. Upon completion of the request, the node (andoperating system) returns a reply to the client 204.

It should be noted that the software “path” through the operating systemlayers described above needed to perform data storage access for aclient request received at node 208.1 may alternatively be implementedin hardware. That is, in an alternate embodiment of the disclosure, thestorage access request data path may be implemented as logic circuitryembodied within a field programmable gate array (FPGA) or an ASIC. Thistype of hardware implementation increases the performance of the fileservice provided by node 208.1 in response to a file system requestissued by client 204.

As used herein, the term “storage operating system” generally refers tothe computer-executable code operable on a computer to perform a storagefunction that manages data access and may, in the case of a node 208.1,implement data access semantics of a general purpose operating system.The storage operating system can also be implemented as a microkernel,an application program operating over a general-purpose operatingsystem, such as UNIX® or Windows XP®, or as a general-purpose operatingsystem with configurable functionality, which is configured for storageapplications as described herein.

In addition, it will be understood to those skilled in the art that theinvention described herein may apply to any type of special-purpose(e.g., file server, filer or storage serving appliance) orgeneral-purpose computer, including a standalone computer or portionthereof, embodied as or including a storage system. Moreover, theteachings of this disclosure can be adapted to a variety of storagesystem architectures including, but not limited to, a network-attachedstorage environment, a storage area network and a disk assemblydirectly-attached to a client or host computer. The term “storagesystem” should therefore be taken broadly to include such arrangementsin addition to any subsystems configured to perform a storage functionand associated with other equipment or systems. It should be noted thatwhile this description is written in terms of a write any where filesystem, the teachings of the present invention may be utilized with anysuitable file system, including a write in place file system.

FIG. 3C depicts three exemplary aggregates 392A, 392B, 392C, which canbe stored on one or more of the disks 212.1-212.3 of the clusteredstorage server system 202 (see FIG. 2). As shown in FIG. 3C, each of theaggregates 392A, 392B, 392C contains two representative volumes, inwhich each volume comprises a storage system subtree. Specifically, theaggregate 392A contains two volumes vol1, vol2; the aggregate 392Bcontains two volumes RT, vol3; and the aggregate 392C contains twovolumes vol4, vol5. In the clustered storage server system 202, thenames of the volumes from the plurality of nodes 208.1-208.3 are linkedinto a global namespace, allowing the client systems 204.1-204.2 tomount the volumes from one of the nodes 208.1-208.3 with a high level offlexibility.

FIG. 3D depicts an exemplary global namespace 394 composed of thevolumes RT, vol1, vol2, vol3, vol4, vol5. The global namespace 394 maybe maintained by storage operating system and may be used in a clusterenvironment, for example, 200, FIG. 2. In the global namespace 394, eachvolume RT, vol1-vol5 represents a virtualized container storing aportion of the global namespace 394 descending from a single rootdirectory. The volumes RT, vol1-vol5 are linked together in the globalnamespace 394 through a number of junctions. A junction is an internalmount point which, to a client, resolves to a directory (which would bethe root directory of the target volume). Such a junction can appearanywhere in a volume, and can link a volume to the root directory ofanother volume. For example, in the clustered system 202, a junction inthe volume vol3 associated with the D-module 216.2 links that volume tothe root directory of the volume vol4, which is associated with theD-module 216.3. A junction can therefore link a volume on one of theD-modules 216.1-216.3 to another volume on a different one of theD-modules 216.1-216.3.

As shown in FIG. 3D, the global namespace 394 includes the volume RT(i.e., the root volume), which has three junctions linking the volume RTto the volumes vol1, vol2, vol3. The global namespace 394 furtherincludes the volume vol3, which has two junctions linking the volumevol3 to the volumes vol4, vol5.

As shown in FIGS. 3C and 3D, data containers and the metadata associatedwith the data containers may be spread out among various volumes. Inorder to get information regarding data containers, storage usage andother user queries that rely on metadata information, one has totraverse the namespace and evaluate individual directory entries.Catalog module 119, as described below in detail efficiently organizesthe metadata in a searchable data structure such that metadata can beeasily searched and hence utilized to process user requests.

Catalog System:

FIG. 4A shows an example of a catalog system 400 (may also be referredto as system 400) that collects metadata for a plurality of datacontainers, organizes the metadata (jointly referred to as“cataloging”), and then provides user requested information pertainingto the data containers, according to one embodiment. As described below,system 400 may include various modules some of which may be executed bythe management console, the storage system as well as at the clientlevel.

System 400 includes a catalog module 401 (similar to catalog module 119,FIG. 1B) that may be executed by or integrated with M-host 218 for aclustered environment 200 (FIG. 2) or operates as module (for example,119, FIG. 1B) of management application 118 for storage environment 100(FIG. 1A). Catalog module 401 includes a catalog controller module (alsoreferred to as “catalog controller”) 410 that interfaces with variousmodules and implements various cataloging related process steps, asdescribed below.

Catalog controller 410 interfaces with a configuration module 408 thatstores configuration information regarding cataloging metadata for aplurality of data containers at one or more data volumes. Configurationinformation may include information regarding how often metadata may becollected, frequency and manner for indexing the collected data as wellas details regarding any actions/reports that a user may seek based onthe collected metadata. Configuration module 408 may be a memory modulethat is accessible by catalog controller 410.

Catalog module 401 may also include a catalog scheduler 406 thatinterfaces with catalog controller 410 and schedules cataloging jobs.The cataloging jobs may include collecting metadata, arranging orindexing the collected metadata, generating reports based on collectedand indexed metadata data, performing a search based on a user request,as well as taking an action based on the search results.

In one embodiment, catalog scheduler 406 receives a client request ormay create a job request based on configuration information stored atconfiguration module 408. The job request may be for collectingmetadata, arranging or indexing the collected metadata, generatingreports based on the collected and indexed metadata data and performinga search based on a user request.

System 400 may further include metadata collection module 416 (may alsobe referred to as a metadata collector module), a pre-processing module412 and a database engine 411. Metadata collection module 416 is used tocollect metadata from operating system 300 for a plurality of datacontainers stored at a data volume, for example, 418. The structure andoperation of metadata collection module 416 depends on the storageenvironment. For example, in one embodiment, in storage environment 100,an instance of metadata collection module 416 may be a part of storagesystem 108. In this example, metadata collection module 416 interfaceswith the file system 302 and obtains metadata regarding a plurality ofdata containers stored in within volume 418.

In another embodiment, for storage environment 200, metadata collectionmodule 416 may be executed at each node 208. In this example, metadatacollection module 416 interfaces with each D-blade 216 to collectmetadata for a plurality of data containers that may be stored within avolume accessible to each node 208.

The information collected by metadata collector 416 depends on userneeds and how system 400 is configured. An example of the type ofinformation that is collected is provided below.

In one embodiment, metadata is collected for an initial version of theplurality of data containers. This may be referred to as “baseline”metadata information (or baseline image). Storage environments typicallymaintain a snapshot of the file system and the associated datacontainers. A file system manager (302, FIG. 3A) or any other module maytake the actual snapshot and communicate it to catalog controller 410.The snapshots being a point in time copy of the file system may be usedto restore a storage file system to an instance when the snapshot wastaken.

A first snapshot for a data volume operates as a starting point and oncethat is created, metadata for data containers that may have changedafter the first snapshot is collected and processed. One process thatmay be used to obtain differential information is called “SnapDiff” thatis provided by NetApp Inc. the assignee of the present application.Metadata collection module 416 may use the SnapDiff process to firstobtain baseline metadata information for the plurality of datacontainers that may be stored in data volume 418. Once the baseline isestablished, metadata collection module 416 may only collect informationfor data containers that may have been created, modified or deleted fromthe baseline snapshot. If there are no changes to data containers afterthe baseline image, then metadata for those data containers is notcollected. It is noteworthy that system 400 may establish any snapshotto be a baseline and then collect incremental metadata for datacontainers that are modified or created after the baseline isestablished.

Metadata collection module 416 provides the collected metadata tocatalog controller 410 via an interface 409 (similar to interface 301,FIG. 3A). The collected metadata is initially handled by pre-processingmodule 412 that receives the metadata and stores it in an intermediatedata structure (may also be referred to as staging table or intermediatetable) 413. Information from the intermediate table 413 is then used bydatabase engine 411 for populating database 414 in a catalog volume 415.It is noteworthy that although pre-processing module 412 is shown as aseparate module, it could be implemented as part of database engine 411.

The following provides an example of what information is collected,pre-processed and stored in intermediate table 413 and then stored indatabase 414 as a searchable data structure.

Metadata collection module 416 may collect the following informationfrom file system 302:

(a) Unique data container identifier, for example, an inode number; (b)a data container type, i.e. if the data container is a directory, fileand others; (c) information regarding whether the data container wasaccessed, created, modified or deleted; (d) a data container name (forexample, NFS file name and CIFS file name) and path; (e) an owneridentifier, for example, an NFS user identifier (UID) or a CIFS owneridentifier; (f) a group identifier, for example, an NFS group identifier(GID); (g) a data container size; (h) permissions associated with thedata container, for example, NFS permission bits that provideinformation regarding permissions associated with the data container;(i) time the data container was accessed (access time); (j) time thedata container was modified (modification time); (k) time the datacontainer was created (creation time), when applicable; and (l) anyother user specified fields.

The pre-processing module 412 takes the foregoing information, extractsa plurality of fields and populates them in intermediate data structure413. For example, pre-processing module 412, extracts the uniqueidentifier value, the NFS and CIFS accessible path where the datacontainer resides, data container name (i.e. NFS and CIFS accessiblename), and extension of the data container that identifies a property ofthe container, for example, if a data container is a data file xyz.doc,then the pre-processing module extracts the “.doc”.

The pre-processing module 412 also extracts information to identify thedata container type, i.e. a file, directory or others, creation time ofthe data container, last time it was accessed and modified, ifapplicable. The pre-processing module 412 separates UID, GID, permissionbits and the size of the data container.

In case the data container is a part of a directory and a snapshot, thepre-processing module 416 generates a unique identifier that identifiesthe snapshot. The pre-processing module 412 also generates a flag thatidentifies whether the data container was created, modified or deleted.

Once the intermediate table 413 is populated, database engine 411 takesthat information and then either creates database 414, if one does notexist or modifies an exiting database 414. In one embodiment, database414 may be a relational database that includes one or more components.Database 414 may include a plurality of searchable segments that aredescribed below in detail. A user may request information regarding datacontainers and catalog module 401 provides user requested informationusing database 414.

A reporting module 407 is also provided such that user requestedinformation may be compiled into reports. The layout and structure ofthe report will depend on the user needs and the user preferences. Theuser may set these reporting preferences using management application118 via a user interface.

Before describing the details of database 414, the following provides anexample of using catalog system 400 in storage environment 429 (similarto 200) as shown in FIG. 4B, according to one embodiment. Each node instorage environment 429 may execute an instance of catalog module 401that is described above with respect to FIG. 4A. Each node may alsoexecute an instance of metadata collection module 416 (shown as C416.1-416.n) to collect metadata from D-blades 216.1-216.n.

Storage environment 429 includes a plurality of volumes, namely 430a-430 g. Volumes 430 a and 430 b are managed by D1 216.1, volumes 430c-430 e are managed by D2 216.2 and volumes 430 f and 430 g are managedby Dn 216.n. The volumes in storage environment 429 may be provided todifferent virtual servers via VIFs 431, 433, 435 and 437. For example,VIF 431 provides access to volume 430 d, VIF 433 provides access tovolume 430 c, VIF 435 provides access to volume 430 d and VIF 437provides access to volume 430 f. Catalog module 401 manages metadata forthe various vservers as if they were individual nodes.

Metadata collection module 416.1 collects metadata for volumes 430 a and430 b. Catalog module 401 at node 208.1 then preprocesses the metadataand stores it at catalog volume 432 a. Metadata collection module 416.2collects metadata for volumes 430 c-430 e. The collected andpre-processed metadata is then stored at catalog volume 434. Similarly,metadata collection module 416.n collects metadata for volumes 430 f and430 g which is then stored at catalog volumes 432 b.

In one embodiment, a query involving metadata stored at differentcatalog volumes (for example, 432 a, 432 b and 434) may be generated.The catalog module at the node where the query is generated, gathersmetadata from different catalog volumes and then the results areaggregated together and presented, as requested by the query. Forexample, when catalog module at node 208.2 receives a request forinformation regarding data containers stored at volumes 430 a-430 g,then catalog module 401 gathers information from catalog volumes 432 a,432 b and 434 and presents the aggregated information to the user.

It is noteworthy that the systems disclosed herein, for example, 429 arescalable. Based on storage space utilization and overall performance,one can assign any volume to operate as a catalog volume. One can alsoadd new catalog volumes to store metadata. Furthermore, a same volumemay be configured to store data containers and metadata.

FIG. 4C shows an example of a data structure 440 (may also be referredto as snapshot table 440) having a plurality of columns that may be usedby database engine 411 to index metadata for database tables 414.Snapshot table 440 may be a stand-alone table or integrated withdatabase 414. Table 440 may also be stored on a per-volume basis on eachcatalog volumes, for example, 432 a-b and 434, as shown in FIG. 4A.

Snapshot table 440 may include a plurality of fields' 440A-440F. Field440A (ID) may be used to identify a snapshot itself. Field 440B (NAME)may be used to name the snapshot. Field 440C (Creation Time) may be usedto store the time when the snapshot was taken. Field 440D(Index_Start_Time) stores a time when metadata collected for aparticular snapshot was indexed. Field 440E (Index_End_Time) may be usedto store a time when information for the snapshot was indexed.

The metadata for a particular snapshot may be indexed based on aschedule that may be established by a user during storage systemconfiguration, a request generated by the user, initiated by amanagement application based on whether the overall storage system isbusy doing other tasks or if the system is idle. The indexing itself canbe optimized such that it does not negatively impact the overallperformance of the storage environment.

Field 440F (ATTR) may be used to store attribute information regarding asnapshot. For example, field 440F may include a snapshot versionindicator indicating a snapshot when a change in status for the datacontainer was discovered.

Besides the fields shown in FIG. 4C, other fields may also be added. Onesuch field may be referred to as a “tag”. A tag is a user defined fieldthat one can add, for example, a user may want to identify all filesthat are labeled as “confidential” by using a “confidential” tag. Thesystems and processes described herein allow one to search for metadatabased on the tags.

Table 440 may be used to determine if there are any snapshots. Thesnapshots itself may be taken by the file system manager 302 (or anyother module) and communicated to the catalog module via cataloginterface 301 (See FIG. 3A). In one embodiment, whenever a snapshot istaken, file system manager 302 may send a notification to the catalogmodule.

When the first snapshot is taken, then metadata collected for thatsnapshot may be used as a baseline image for database table 414 (FIG.4A), as described below. As more snapshots are taken, metadata for datacontainers that were created, modified or deleted from the initialsnapshot is collected and indexed, as described below. If there is nochange in the data containers after the initial snapshot, then nometadata is collected for the unchanged data containers.

FIGS. 4D and 4E show examples of data structures of database 414generated by database engine 411 of catalog module 401, according to oneembodiment. Database 414 may be a relational database having a pluralityof searchable segments that logically interface with each other. Forexample, database 414 may include a directories table 450 and a datacontainer table 452. The first searchable segment, a directory table450, which may include information regarding all the directories for adata volume that is configured to be cataloged, for example, 418 (FIG.4A). Directory table 450 may include a plurality of fields' 450A-450Mthat are now described below.

Field 450A (Identifier) may be a unique identifier to identify adirectory, for example, an inode number, an inode generation number orboth. Field 450B (Parent) identifies a “parent” for the directory. Theparent in this case is an upper level directory to which the directoryidentified by 450A may belong. Field 450C provides a directory path.

Field 450D provides a name for the directory. Field 450E provides adirectory size. Field 450F (Mode) provides the permissions associatedwith a directory. The permissions indicate what level of authority auser has with respect to a particular directory. Permissions may rangefrom being able to read the directory entry to be able to create, modifyor delete the entry and other permission types.

Field 450G identifies the owner of the directory, shown as “uid”. Field450H identifies a group to which the directory may belong to, shown as“Gid”. In an enterprise having different business groups, for example,engineering, sales, marketing legal and others, a storage system may bedivided among different entities. Field 450H identifies the group towhich a particular directory belongs.

Field 450I (Atime) provides a time when the directory was last accessed,while field 450J (Ctime) provides a time when the directory was created.Field 450K (Mtime) includes a time when the directory was modified.Field 450L includes a flag that indicates whether an entry was added (byusing a flag “A”), modified (by using a flag “M”) or deleted (by using aflag “D”).

Field 450M identifies a snapshot to which the directory may belong. Thismay be similar to field 440A shown in FIG. 4C.

Database 414 may also include a second searchable segment, for example,a data container table that may store metadata information regarding aplurality of data containers. FIG. 4E shows an example of data containertable 452 that stores information regarding a plurality of datacontainers, for example, files. Each file in the data container table452 is associated with an entry in the directories table 450. Thisallows one to include a path for a file only once in the directoriestable and one does not have to copy the path in data container table 452every time the metadata for the file is indexed.

Data container table 452 may include various fields 452A-452L. Field452A identifies the file with a unique identifier, for example, an inodenumber, an inode generation number or both. Field 452B associates aparent to the data container identified by field 452A. This field mapsto an entry in the directory table 450. Because of this cross referenceto the directory table, one does not have to enter the data containerpath for all individual data container entries. This saves memory spaceand processing time. For example, if there are one million files in astorage system, if one tried to save the paths for all one millionfiles, it would take space and processing time. Instead, in oneembodiment, field 452B cross references to a directory entry in datastructure 450 where the path for each entry in data structure 452 islocated.

In another embodiment, the structure of cross-referencing files todirectory entry also reduces processing time when a directory isrenamed. For example, if each file had an entry that provided thestorage path and directory name, then one would have to go and changeentries for each individual files. Using the foregoing scheme, one onlyhas to update directory names and individual path entries do not need tobe updated.

Field 452C includes a data container name, for example, a file name,while field 452D includes a size of the data container. Field 452E(Mode) identifies the permissions that may be associated with the datacontainer. This includes, whether a user is permitted to simply read thedata container content, modify it or delete it.

Field 452F (UID) identifies the owner of the data container, while field452G (GID) identifies the group to which the data container belongs.

Field 452H (Atime) identifies the time the data container is accessed,field 452I (Ctime) identifies the time it was created, while field 452J(Mtime) identifies the time the data container was modified, ifapplicable. Field 452K is a flag that indicates whether the datacontainer was created (A), modified (M) or deleted (D). Field 452Lidentifies the snapshot, if applicable to which the file belongs. Thisidentifier is similar to 450M in table 450.

The following example explains the various entries of FIGS. 4D and 4E:Directories “a” and “b” are identified as 10 and 20 by identifier 405Ain FIG. 4D. Directories “a” and “b” are parent directories as shown bydirectory path 450C entry “/”. Directories “c” and “d” are identified as30 and 40 and are sub-directories under parent directory “a”.

File f.txt as identified by file name 452C (FIG. 4E) is stored at“/a/c”. The path can be obtained by using the cross referenced parentdirectory entry 30 under 452B (FIG. 4E). Files g.txt, h.doc, i.epp andj.pdf as identified by file name 452B are stored at “/a/d” as shown bythe parent identifier 30. File e.jpeg is stored under sub-directory “b”based on parent identifier 20.

It is noteworthy that although FIGS. 4D and 4E show examples ofdifferent database tables 450 and 452, the adaptive embodiments are notlimited to having separate tables. In one embodiment, the files anddirectory tables 450 and 452 may be included in a single table butdifferentiated by an identifier, for example, a Snapshot identifier.

FIG. 4F shows an example of populating directory and data containertables at time t0 and time t1. The directory table at time t0 identifiesthe inodes 10, 20, 30 and 40 under field 450A. The parent fields arespecified as 0, 0, 10 and 10 under field 450B. The directory path isshown as /, /, /a/ and /a/ under field 450C. The names of thedirectories are provided as “a”, “b”, “c” and “d” under field 450D.

The files or data containers at time t0 are also shown in the datacontainer table labeled as Files0. For example, field 452A provides theinode numbers 31, 41, 42, 43, 44 and 51 for files f.txt, g.txt, h.doc,i.cpp, j.pdf and e.jpeg, respectively. Each file is associated with aparent under field 452B, i.e. 30, 40, 40, 40, 40 and 20 respectively.

At time t1, another snapshot is taken and metadata for the snapshot attime t1 (may be referred to as Snap1) is shown as 450′ and 452′. UnderSnap1, directory z gets created under /b/ as indicated by the flag “A”which means added, directory c is moved from /a/c to /b/c and directory/a/d is modified.

In the Files1 table, at Snap1, file y.txt is created under /b/z, filej.pdf is modified and file h.doc is deleted.

In one embodiment, database segments 450 and 452 may be used efficientlyto respond to user queries for information regarding data containersthat can obtained by searching metadata information. Since metadatafields are organized in a relational database, one can search throughthe database to provide user requested information. The information typeof course may vary based on a user request.

As shown above, database 414 is split into multiple logical tables 450and 452. This is efficient and saves disk space because the datacontainer tables (or file tables) do not include the path for every fileentry and this saves storage space. Instead, each data container (forexample, a file) is associated with a parent (or directory) identifierin a directories table. To access a data container, one simply has tolook at the parent entry and ascertain the path where the data containeris stored.

Process Flow:

FIG. 5A shows a block diagram for using system 400 for collectingmetadata, pre-processing and indexing the pre-processed metadata tobuild database 414, according to one embodiment. The process begins inblock S500 when a storage volume is configured to operate as a catalogvolume. A storage administrator having appropriate permissions and usingmanagement application 118 configures the storage volume as a catalogvolume (for example, 415 (FIG. 4A) to store database 414.

The storage administrator may also configure one or more data volumes,for example, 418 (FIG. 4A) or 430 a-430 g (FIG. 4B) such that metadatafor the data containers stored at the data volumes can be collected,indexed and then stored at the catalog volume. The storage administratormay associate one or more data volumes to a particular catalog volume.The storage administrator may specify a collection frequency whichdetermines how often the metadata is collected. The storageadministrator may also specify certain events based on which themetadata may be collected. For example, the storage administrator mayspecify that when a new snapshot is taken, metadata should be collectedfor the data containers that may have changed from a previous snapshotof the same data volume.

In block S502, metadata is collected by metadata collection module 416.In one embodiment, metadata is collected based on a user specifiedschedule as described above. In another instance, metadata may becollected based on an event, for example, a snapshot. In yet anotherembodiment, a user may send a request to collect metadata for a datavolume.

The metadata that is collected by metadata collection module 416 may befor a baseline snapshot. This means that metadata is collected for allthe data containers stored at the data volume. When there are changes tothe data containers and a snapshot is taken at a later instance, thenmetadata is collected for only the changed data containers. Incrementalmetadata collection is efficient because one does not have to repeat themetadata collection step for all the data containers including datacontainers that may not have changed from a previous instance.

In one embodiment, for a clustered environment, the metadata collectionmodule 416 is executed at one or more nodes and collects metadataassociated with data volumes that are accessible to the node. Themetadata may be collected from operating system 300 that maintainsinformation regarding all the data containers at the selected datavolume.

After the metadata is collected, it is pre-processed and placed atintermediate table 413 in block S504. One reason for pre-processing themetadata is because the metadata received from the operating system maybe of a different format and one may have to extract one or more fieldsso that the information can be placed in database 414 and usedefficiently to respond to user requests as described below. An exampleof how fields are extracted from the collected metadata and placed atintermediate table 413 has been described above.

After the metadata is pre-processed, the information from intermediatetable 413 is indexed. The indexing is based on one or more fields thathave been described above with respect to the database 414 tables.

The indexing in block S506 may be based on a policy that is set up by auser and stored in configuration module 408 (FIG. 4A). The policy allowsa user to set indexing of metadata collected after each snapshot. Theindexing may be “on-demand” i.e. based on when a user or storageadministrator sends a request to start indexing. In another embodiment,indexing may be time based such that catalog controller 410 startsindexing based on a set schedule. The indexing policy settings make thesystem and process flexible because users in different storageenvironments may use different polices for indexing metadata based onuser needs.

After the pre-processed metadata is indexed, in block 506, it is storedin database 414. In one embodiment, the stored metadata is placed in asearchable relational database 414. An example, of searchable database414 is described above with respect to FIGS. 4C-4F.

In one embodiment, for a clustered environment, database 414 may bestored at one or more volumes that may be referred to as catalogvolumes. Metadata collected from different nodes may be stored at thecatalog volumes. Catalog controller 410 can access a volume locatordatabase (VLDB) 403 (FIG. 4A) (or 220, FIG. 2A) that identifiesdifferent volumes and their locations. This allows the catalogcontroller to cross reference the volume identifiers with the collectedmetadata.

FIG. 5B shows a process flow diagram for handling query requests usingdatabase 414, according to one embodiment. The process begins in blockS508 when a user request is received by catalog module 401. The userrequest may be received via a user interface that is provided by client402 (FIG. 4A). The request is received by catalog interface 404 andforwarded to scheduler 406. Scheduler 406 may maintain one or morequeues for receiving user requests. The user request is then forwardedto catalog controller 410. In another embodiment, the query may bescheduled by the user based on a specified duration or an event, asdescribed above.

In block S510, the query is forwarded to database engine 411 so thatuser requested information can be obtained from database 414. Catalogcontroller 410 parses the user request to ascertain what fields indatabase 414 may need to be searched. For example, if the user wants toknow how many “.pdf” files belong to a particular group, then catalogcontroller will search file name 452C and group identifier 452G torespond to the query.

In block S512, the user requested information is presented to the user.The information may be displayed in a user interface on a displaydevice. The information may be presented as a report by reporting module407.

In block S514, an action that may need to be taken, based on the searchresults is performed. The nature and action type may be based on userrequest. For example, a user request may be to obtain informationregarding certain file types for example, video files. The actionassociated with the file type may be to move the certain file type fromone volume to another volume. Catalog controller 410 obtains the filetypes by searching database 414 that stores information regarding filetypes. Thereafter, catalog controller communicates with operating system300 to move the files from the first location to one or more locations.This example is provided to illustrate the adaptive nature of thevarious embodiments and not to limit the various embodiments shownherein.

FIG. 5C shows a process flow diagram for collecting metadata and thenprocessing user requests in a clustered system, according to oneembodiment. The process begins in block S516 when a storage volume isconfigured for collecting metadata. Referring back to FIG. 4C, thedifferent volumes 430 a-430 g associated with different virtual serversmay be configured to collect metadata.

In block S518, metadata is collected from a plurality of nodes. Themetadata is collected by metadata collection module 416 executed by theplurality of nodes and then stored at one or more catalog volumes (432a, 432 b and 434, FIG. 4B). An example, of this is shown in FIG. 4B,where metadata collection modules 416.1-416.N are executed at each nodeand collect metadata for data volumes that are configured in block S516.

In block S520, metadata collected from different volumes and controlledby different nodes is pre-processed and stored in database 414 atcatalog volume 434 (FIG. 4B). The pre-processing is performed so thatinformation from the collected metadata can be used to populate database414. The collected metadata may arrive in an order determined by thestorage operating system. The collected metadata may include moreinformation than what may be needed by catalog module 401. Thepre-processing is performed such that catalog module can extract therelevant fields and values that are used in database 414. Detailsregarding pre-processing and database 414 are provided above withrespect to FIGS. 4A-4F and FIGS. 5A-5B.

In block S522, a user query for information regarding a plurality ofdata structures that may be stored at different volumes and controlledby different nodes is received. The user query is received by catalogmodule 410 via a user interface provided by management application 118.A user may request different information types for the plurality of datastructures. The type of user query and the nature of information thatthe user may seek depends on how a user is using storage environment200.

In block S524, database 414 is used to search for information requestedby the user. Searching database 414 is faster and less taxing oncomputing resources vis-à-vis performing a directory “walk” analyzingmetadata for millions of files. For example, to determine how many fileswere accessed within certain duration, one only has to search usingfield 452G and ascertain the number of files within the specifiedduration. One is able to do that because of the way database 414 isstructured and built.

In some instances, an action may be associated with a search query. Whenan action is associated with a search query, then the requested actionassociated with the search results is performed in block S526. Forexample, a user may configure a volume such that after every snapshot,certain file types may be moved to another location. To accommodate thisaction, after every snapshot, first database 414 is searched toascertain the file types and then operating system 300 is notified tomove the file types.

In one embodiment, using catalog system 400 and the process stepsdescribed above, one can efficiently search metadata for data containersstored at one or more data volumes both in a clustered environment 200and non-cluster environment 100. In traditional storage environments,the operating system is typically geared towards handling access to oneobject at a time. Access to a group of files within a file system isdifficult. Furthermore, the operating system layout is such thatmetadata for a data container, for example, a file name, attributes,access control lists, information regarding the owner may not be storedcontiguously at the storage devices. Therefore, to access informationregarding a data container or a group of data containers, one has totraverse through a namespace and perform a directory search.

The embodiments disclosed herein efficiently search for data containersusing relational database 414 and its associated tables. For example,one can search for “all files greater than size 1 MB that were notaccessed within the last year” by searching data structure 452. One canuse the size field 452D and access time field 452H to filter all filesthat may be greater than 1 MB and were not accessed within one year,without having to do an extensive namespace based directory search.

In one embodiment, catalog system 400 integrates metadata managementrelated operations as well as data container related operations within astorage environment. In conventional systems, typically, one vendorprovides an operating system 300 and a different vendor provides aseparate system for handling metadata related operations. Catalog system400 is integrated with operating system 300 and management application118. Hence, one does not need to use another third party module forhandling metadata related operations.

In one embodiment, metadata related operations are executed efficientlybecause catalog system 400 is integrated with operating system 300. Thisallows one to use operating system 300's ability to collect metadataefficiently. If one were to use an external, third party system, thenone will have to scan an entire file system using other techniques,compared to the techniques that are integrated with the operatingsystem.

In one embodiment, because metadata is handled efficiently, one canprovide useful reports to users such that users can efficiently use thestorage space. The reports are provided by reporting module 407 andmanagement application 118 via a user interface. The data for thereports is provided by catalog module 401 and formatted and presented bymanagement application 118.

Reports can be configured based on user specified parameters, forexample, users may want to know what different types of files are beingused, for example, media files, “.doc” files and others. In conventionalsystems, to gather that information, one will have to traverse through anamespace/directory that may include millions of files. In theembodiments disclosed herein, one can obtain this information fromdatabase 414 by searching field 452C that includes the file type. Thisis faster and more efficient than searching through a directory that mayinclude millions of files.

The embodiments herein also allow a user to generate reports based ondifferent users that use the storage space. For example, by searchingdatabase 414 using fields 452C and owner identification field 452F, onecan ascertain which users are using a certain file type. One can alsoview usage of storage space based on groups, by using the groupidentifier 452G. One can do this efficiently because of the manner inwhich the relational database 414 is structured.

In another embodiment, reports can be generated based on volumes thatare spread out in a clustered environment 200. Because metadata iscollected for different nodes and efficiently cataloged at one or morecatalog volumes (for example, 434, FIG. 4B), one is able to obtain anoverall view of the clustered system, as well as node based view. Astorage administrator can issue cluster wide requests and catalog modulecan obtain information regarding the entire cluster or for specificvolumes. One can obtain all this information without having to performan entire file system search that can be resource intensive andinefficient.

In yet another embodiment, not only one can generate reports and performfast queries, one can also perform actions that may be related to thesearch results. For example, a user may want to know how many files of acertain type, for example, .mp3, are saved in the storage system andthen move the files to a different storage environment. One can conductan efficient search using database 414 and then perform the appropriateaction. This allows a user to efficiently use storage space. Continuingwith the foregoing example, if the .mp3 files are not being accessed orused frequently and the user has access to secondary storage that isalso not used frequently, then the user can move the files to thesecondary storage that is used infrequently.

This allows a user to efficiently manage and use storage resources. Theuser can obtain storage system usage views efficiently by using database414 and based on user needs perform the appropriate actions for movinginformation around.

The embodiments disclosed herein allow a user to search for datacontainers based on a data container owner, name of the data container,modification time, access time and type of data container and otherfields. The search may be performed by combining different fields. Forexample, a user can search which owners and groups use the highestamount of storage as well as the least amount of storage. One can thenapportion storage cost to individuals, teams and business units.

Since metadata is collected incrementally for different snapshots, onecan look at the growth of storage between snapshots. This will allowstorage administrators to plan better for upgrading or downgradingstorage space, based on business need.

It is noteworthy that the systems and processes described herein are notlimited to collecting metadata for Snapshots but instead catalog modulemay catalog metadata for an active file system.

Storage System Node:

FIG. 6 is a block diagram of a node 208.1 (FIG. 2) that isillustratively embodied as a storage system comprising of a plurality ofprocessors 602A and 602B, a memory 604, a network adapter 610, a clusteraccess adapter 612, a storage adapter 616 and local storage 613interconnected by a system bus 608. The local storage 613 comprises oneor more storage devices, such as disks, utilized by the node to locallystore configuration information (e.g., in a configuration table 614).

The cluster access adapter 612 comprises a plurality of ports adapted tocouple node 208.1 to other nodes of cluster 202. In the illustrativeembodiment, Ethernet may be used as the clustering protocol andinterconnect media, although it will be apparent to those skilled in theart that other types of protocols and interconnects may be utilizedwithin the cluster architecture described herein. In alternateembodiments where the N-modules and D-modules are implemented onseparate storage systems or computers, the cluster access adapter 612 isutilized by the N/D-module for communicating with other N/D-modules inthe cluster 202.

Each node 208.1 is illustratively embodied as a dual processor storagesystem executing a storage operating system 606 that preferablyimplements a high-level module, such as a file system, to logicallyorganize the information as a hierarchical structure of nameddirectories, files and special types of files called virtual disks(hereinafter generally “blocks”) on disks 212.1. However, it will beapparent to those of ordinary skill in the art that the node 208.1 mayalternatively comprise a single or more than two processor systems.Illustratively, one processor 602A executes the functions of theN-module 214.1 on the node, while the other processor 602B executes thefunctions of the D-module 216.1.

The memory 604 illustratively comprises storage locations that areaddressable by the processors and adapters for storing programmableinstructions and data structures. The processor and adapters may, inturn, comprise processing elements and/or logic circuitry configured toexecute the programmable instructions and manipulate the datastructures. It will be apparent to those skilled in the art that otherprocessing and memory means, including various computer readable media,may be used for storing and executing program instructions pertaining tothe invention described herein.

The storage operating system 300, portions of which is typicallyresident in memory and executed by the processing elements, functionallyorganizes the node 208.1 by, inter alia, invoking storage operations insupport of the storage service implemented by the node. An example ofoperating system 300 is the DATA ONTAP® (Registered trademark of NetApp,Inc.) operating system available from NetApp, Inc. that implements aWrite Anywhere File Layout (WAFL® (Registered trademark of NetApp,Inc.)) file system. However, it is expressly contemplated that anyappropriate storage operating system may be enhanced for use inaccordance with the inventive principles described herein. As such,where the term “ONTAP” is employed, it should be taken broadly to referto any storage operating system that is otherwise adaptable to theteachings of this invention.

The network adapter 610 comprises a plurality of ports adapted to couplethe node 208.1 to one or more clients 204.1/204.2 over point-to-pointlinks, wide area networks, virtual private networks implemented over apublic network (Internet) or a shared local area network. The networkadapter 610 thus may comprise the mechanical, electrical and signalingcircuitry needed to connect the node to the network. Illustratively, thecomputer network 106 may be embodied as an Ethernet network or a FibreChannel (FC) network. Each client 204.1/204.2 may communicate with thenode over network 106 by exchanging discrete frames or packets of dataaccording to pre-defined protocols, such as TCP/IP.

The storage adapter 616 cooperates with the storage operating system 300executing on the node 208.1 to access information requested by theclients. The information may be stored on any type of attached array ofwritable storage device media such as video tape, optical, DVD, magnetictape, bubble memory, electronic random access memory, micro-electromechanical and any other similar media adapted to store information,including data and parity information. However, as illustrativelydescribed herein, the information is preferably stored on disks 212.1.The storage adapter 616 comprises a plurality of ports havinginput/output (I/O) interface circuitry that couples to the disks over anI/O interconnect arrangement, such as a conventional high-performance,FC link topology.

Storage of information on each array 212.1 is preferably implemented asone or more storage volumes that comprise a collection of physicalstorage disks 212.1 cooperating to define an overall logical arrangementof volume block number (vbn) space on the volume(s). Each logical volumeis generally, although not necessarily, associated with its own filesystem. The disks within a logical volume/file system are typicallyorganized as one or more groups, wherein each group may be operated as aRAID. Most RAID implementations, such as a RAID-4 level implementation,enhance the reliability/integrity of data storage through the redundantwriting of data “stripes” across a given number of physical disks in theRAID group, and the appropriate storing of parity information withrespect to the striped data. An illustrative example of a RAIDimplementation is a RAID-4 level implementation, although it should beunderstood that other types and levels of RAID implementations may beused in accordance with the inventive principles described herein.

Processing System:

FIG. 7 is a high-level block diagram showing an example of thearchitecture of a processing system, at a high level, in which theexecutable instructions described above can be implemented. Theprocessing system 700 can represent management console 120, for example.Note that certain standard and well-known components which are notgermane to the present invention are not shown in FIG. 7.

The processing system 700 includes one or more processors 702 and memory704, coupled to a bus system 705. The bus system 705 shown in FIG. 7 isan abstraction that represents any one or more separate physical busesand/or point-to-point connections, connected by appropriate bridges,adapters and/or controllers. The bus system 705, therefore, may include,for example, a system bus, a Peripheral Component Interconnect (PCI)bus, a HyperTransport or industry standard architecture (ISA) bus, asmall computer system interface (SCSI) bus, a universal serial bus(USB), or an Institute of Electrical and Electronics Engineers (IEEE)standard 1394 bus (sometimes referred to as “Firewire”).

The processors 702 are the central processing units (CPUs) of theprocessing system 700 and, thus, control its overall operation. Incertain embodiments, the processors 702 accomplish this by executingexecutable instructions 706 stored in memory 704. A processor 702 maybe, or may include, one or more programmable general-purpose orspecial-purpose microprocessors, digital signal processors (DSPs),programmable controllers, application specific integrated circuits(ASICs), programmable logic devices (PLDs), or the like, or acombination of such devices.

Memory 704 represents any form of random access memory (RAM), read-onlymemory (ROM), flash memory, or the like, or a combination of suchdevices. Memory 704 includes the main memory of the processing system700. Instructions 706 may be used to implement the techniques introducedabove (e.g. catalog module 401) may reside in and executed (byprocessors 702) from memory 704.

Also connected to the processors 702 through the bus system 705 are oneor more internal mass storage devices 710, and a network adapter 712.Internal mass storage devices 710 may be or may include any conventionalmedium for storing large volumes of data in a non-volatile manner, suchas one or more magnetic or optical based disks. The network adapter 712provides the processing system 700 with the ability to communicate withremote devices (e.g., storage servers 202) over a network and may be,for example, an Ethernet adapter, a Fibre Channel adapter, or the like.The processing system 700 also includes one or more input/output (I/O)devices 708 coupled to the bus system 705. The I/O devices 708 mayinclude, for example, a display device, a keyboard, a mouse, etc.

Thus, a method and apparatus for managing metadata for data containershave been described. Note that references throughout this specificationto “one embodiment” or “an embodiment” means that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics being referred to maybe combined as suitable in one or more embodiments of the invention, aswill be recognized by those of ordinary skill in the art.

While the present disclosure is described above with respect to what iscurrently considered its preferred embodiments, it is to be understoodthat the disclosure is not limited to that described above. To thecontrary, the disclosure is intended to cover various modifications andequivalent arrangements within the spirit and scope of the appendedclaims.

What is claimed is:
 1. A machine implemented method for a storagesystem, comprising: configuring a data storage volume for collectingmetadata for a plurality of data containers stored at the data storagevolume when a first snapshot of the data storage volume is generated;wherein the metadata includes an attribute that is associated with theplurality of data containers and the metadata comprises a baseline imagefor a searchable data structure; configuring a storage volume as acatalog volume for storing metadata associated with the plurality ofdata containers; collecting metadata for the plurality of datacontainers by a processor executable metadata collection module executedby the plurality of computing nodes; wherein after the first snapshot isgenerated for the data storage volume, metadata is collected only fordata containers that were changed after the first snapshot wasgenerated; pre-processing the collected metadata by extracting one ormore fields from the collected metadata by a processor executablecatalog module executed by the plurality of computing nodes; and storingthe pre-processed metadata in the searchable data structure forresponding to a user query requesting information regarding theplurality of data containers; wherein the searchable data structure isstored at the catalog volume by the catalog module and includes a firstsearchable segment for storing metadata for a plurality of directoryentries of the data storage volume and a second searchable segment forstoring metadata for non-directory based data containers stored at thestorage volume; and wherein each entry in the second searchable segmentstores a reference to a parent entry in the first searchable segmentsuch that a storage path of each entry in the second searchable segmentcan be obtained from the reference to the parent entry in the firstsearchable segment without having to store individual storage paths forthe non-directory based data containers at the second searchablesegment.
 2. The method of claim 1, wherein the pre-processed metadata isstored in an intermediate data structure prior to being stored in thesearchable data structure.
 3. The method of claim 1, wherein the catalogmodule receives metadata from a metadata collector that interfaces witha file system for the storage system.
 4. The method of claim 1, whereinfor responding to the user query, the first searchable segment storesattributes for the plurality of directory entries including a uniquedirectory identifier, a directory name, a size of a directory, apermission associated with a directory, a user identifier identifying auser that uses a directory, a group identifier identifying a groupassociated with a directory, an access time when a directory wasaccessed, a creation time when a directory was created, a modificationtime when a directory was modified and an indicator indicating if adirectory was created, modified or deleted.
 5. The method of claim 1,wherein for responding to the user query, the second searchable segmentstores attributes for the plurality of data containers, including aunique identifier for identifying a data container, an identifier thatassociates a data container to a directory entry, a data container name,a size of a data container, a permission associated with a datacontainer, a user identifier identifying a user for a data container, agroup identifier identifying a group associated with the data container,an access time when a data container was accessed, a creation time whena data container was created, a modification time when a data containerwas modified and an indicator indicating if a data container wascreated, modified or deleted.
 6. The method of claim 1, wherein inresponse to a user query, catalog module searches the searchable datastructure and obtains information requested in the user query.
 7. Themethod of claim 6, wherein an action is taken based on the obtainedinformation in response to the user query.
 8. The method of claim 1,wherein the searchable data structure stores metadata associated with anactive file system.
 9. The method of claim 1, wherein the catalog volumeand the data storage volume are stored within a same volume.
 10. Themethod of claim 1, wherein a plurality of catalog volumes associatedwith a plurality of data volumes are configured to store metadata fordata containers stored at the plurality of data volumes.
 11. The methodof claim 1, wherein the metadata is collected based on an event, aschedule or a user request.
 12. The method of claim 1, wherein thesearchable data structure includes a snapshot identifier for identifyinga snapshot when the plurality of data containers were replicated; a timestamp when the snapshot was taken; an indicator indicating if a datacontainer was added, deleted or modified and a snapshot versionindicator indicating the snapshot when a change in status for the datacontainer was discovered.
 13. The method of claim 12, wherein a state ofa file system is established for a given snapshot by providing anindicator indicating if a data container was added, deleted or modifiedsince a baseline image.
 14. A machine implemented method for a storagesystem for storing a plurality of data containers at one or more storagevolumes, comprising: pre-processing metadata associated with theplurality of data containers, the metadata including an attribute thatis associated with the plurality of data containers; and generating asearchable data structure by indexing the pre-processed metadata suchthat information related to the plurality of data containers is obtainedregardless of a storage volume location; wherein the search datastructure includes a first searchable segment for storing metadata for aplurality of directory entries and a second searchable segment forstoring metadata for non-directory based data containers; and whereineach entry in the second searchable segment stores a reference to aparent entry in the first searchable segment such that a storage path ofeach entry in the second searchable segment can be obtained from thereference to the parent entry in the first searchable segment withouthaving to store individual storage paths for the non-directory baseddata containers at the second searchable segment.
 15. The method ofclaim 14, further comprising; retrieving information by searching thesearchable data structure based on a request for information related tothe plurality of data containers; and presenting the information inresponse to the request.
 16. The method of claim 15, wherein the requestdefines a duration pertaining to a state of the plurality of datacontainers and at least another attribute for searching the metadata.17. The method of claim 16, wherein the other attribute describes one ormore properties of the plurality of data containers.
 18. The method ofclaim 14, wherein the indexed metadata is stored at a catalog volumethat is managed by a catalog module.
 19. A machine implemented methodfor a storage system for storing a plurality of data containers at oneor more storage volumes, comprising: indexing metadata associated withthe plurality of data containers, the metadata including an attributethat is associated with the plurality of data containers and themetadata is collected from at least one storage volume; and storing theindexed metadata associated with the plurality of data containers in asearchable data structure used for obtaining information regarding theplurality of data containers; wherein the searchable data structure isstored at a catalog volume by a catalog module executed by a pluralityof nodes and includes a first searchable segment for storing metadatafor a plurality of directory entries of the data storage volume and asecond searchable segment for storing metadata for non-directory baseddata containers stored at the storage volume; and wherein each entry inthe second searchable segment stores a reference to a parent entry inthe first searchable segment such that a storage path of each entry inthe second searchable segment can be obtained from the reference to theparent entry in the first searchable segment without having to storeindividual storage paths for the non-directory based data containers atthe second searchable segment; and wherein the searchable data structurestores a snapshot table identifier for identifying a snapshot when theplurality of data containers were replicated and a time stamp when thesnapshot was taken.
 20. The method of claim 19, wherein metadata iscollected to capture a baseline state of a file system that includes theplurality of data containers.
 21. The method of claim 19, wherein afterthe baseline image is created, metadata is collected only for datacontainers that have been created or modified since the baseline image.22. The method of claim 19, wherein a state of a file system isestablished for a given snapshot by providing an indicator indicating ifa data container was added, deleted or modified since the baselineimage.
 23. The method of claim 19, wherein the searchable data structurestores an indicator indicating if a data container was added, deleted ormodified.
 24. The method of claim 19, wherein the search data structurestores a snapshot version indicator indicating the snapshot when achange in status for the data container was discovered.
 25. A machineimplemented method for a storage system for storing a plurality of datacontainers, comprising: preprocessing metadata associated with theplurality of data containers stored at one or more storage volumes, themetadata including an attribute that is associated with the plurality ofdata containers; generating a searchable data structure for storing thepre-processed metadata for gathering information regarding any datacontainer stored at any storage volume; wherein the search datastructure includes a first searchable segment for storing metadata for aplurality of directory entries and a second searchable segment forstoring metadata for non-directory based data containers; and whereineach entry in the second searchable segment stores a reference to aparent entry in the first searchable segment such that a storage path ofeach entry in the second searchable segment can be obtained from thereference to the parent entry in the first searchable segment withouthaving to store individual storage paths for the non-directory baseddata containers at the second searchable segment; searching thesearchable data structure in response to a request for informationrelated to the plurality of data containers; retrieving the requestedinformation from the searchable data structure; and presenting theinformation in response to the request.
 26. The method of claim 25,further comprising: taking an action based on a search result generatedby searching the searchable data structure.
 27. The method of claim 25,wherein a report is presented in response to the request.
 28. The methodof claim 27, wherein the report is specific to a user having access tothe storage system.
 29. The method of claim 27, wherein the report isfor a group of users using the storage system.
 30. The method of claim25, wherein the metadata is stored at a catalog volume that is managedby a catalog module.